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Space Weather Conditions at the Time of the Galaxy 15 Spacecraft Anomaly Report by the NOAA Tiger Team

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Galaxy 15 NOAA Tiger Team • In April 2010, the Galaxy 15 satellite stopped responding to ground commands. • The Space Weather Prediction Center (SWPC) Director formed a NOAA Tiger Team to document the space environmental conditions experienced by the Galaxy 15 spacecraft surrounding the anomaly. • The team was comprised of representatives from SWPC and the NESDIS National Geophysical Data Center (NGDC). • The report was intended to aide ongoing anomaly analysis but does not include any assessment of the space weather conditions on specific satellite components.

OUTLINE Space Weather Conditions – 05 Apr 10 • This presentation follows space weather conditions progressing from the sun to near the Galaxy 15 location showing: • Events that occurred at the sun • Resulting global changes in the near-earth space environment • Local changes near Galaxy 15 in the energetic charged particles that can cause satellite charging and electronic component failure • Summary • Solar activity was elevated but not remarkable • Global geomagnetic activity described by global indices was moderate to extreme • Local measurements near Galaxy 15 show that a large geomagnetic substorm occurred 48 minutes prior to the anomaly. The substorm caused remarkable increases in the measured local flux of energetic particles known to cause surface or internal satellite charging

Space Weather Conditions 1. Events at the Sun (1 of 3) Solar activity prior to the Galaxy 15 anomaly on April 05 at 9:48 was elevated but unremarkable. • On 03 April @ 9:54 UT (2 days prior to the anomaly) a solar B7 flare was observed by the NOAA GOES-14 X-Ray Sensor (XRS) • Flares of this intensity are not usually associated with intense space weather • In solar cycle 23 there were >14,000 flares more intense than a B7-level flare • There have already been 125 flares more intense than B7 in the new cycle Satellite Eclipse B7 FLARE

Space Weather Conditions 1. Events at the Sun (3 of 3) Galaxy 15 anomaly • April 05 07:56 UT – Nearly 2 days after the CME lifted off from the sun, it was observed by the NASA ACE satellite upstream of earth • It takes ~30 minutes for the solar wind to propagate from ACE to Earth • The solar wind magnetic field turned southward (negative) • The solar wind speed increased from ~500 to >700 km/s CME detected by ACE Such solar wind conditions often result in a moderate geomagnetic storm Note: ACE is the NASA Advance Composition Explorer located at the L1 sun-earth Lagrangian point approximately ~1.5x106 km in the sunward direction. Plot shows solar wind parameters observed at ACE, time-shifted to Earth. Data Source: NASA Omni

Space Weather Conditions 2. Global Environment At Earth (1 of 2) Some (but not all) global geomagnetic activity indicators were extreme immediately prior to the anomaly 01 Oct 05 to 01 May 10 Currently only quick look plots are available for April AL index was <-2000 nT prior to the anomaly. Larger values observed only once previously during Galaxy 15 lifetime (launched: 13 Oct 05) Kp index reached 7.7 prior to the anomaly. Larger values were observed only once previously during the Galaxy 15 lifetime However, Dst index reached -32 nT prior to anomaly indicating only a moderate storm – similar to many previously observed levels during the Galaxy 15 lifetime ? Indices provided by the Kyoto World Data Center

Space Weather Conditions Galaxy 15 Anomaly (05 Apr 2010 0948 UT) Statistical Distribution of Spacecraft Anomalies GALAXY 15 anomaly occurred in the midnight to dawn local time sector, where anomalies are most likely to be observed. GALAXY 15 anomaly occurred near equinox which is the time of year where anomalies are most likely to occur Around equinox is also the time of year where geosynchronous spacecraft encounter eclipse periods and elevated geomagnetic activity